Dominik Szwajgier, Anna Jakubczyk

Background. Lactic acid bacteria (LAB) were pointed out to produce ferulic acid esterase. Except the release of phenolic acids from esterified forms, it was postulated that the biotransformations of these compounds can occur during the bacterial growth. In the presented work, the biotransformation of ferulic acid by Lactobacillus acidophilus K1 and three Bifidibacterium strains (B.animalis Bi30, B. catenulatum KD 14 and B. longum KN 29) was studied.

Material and methods. The microorganisms were grown in media containing methyl esters of phenolic acids as carbon sources. The feruloyl esterase activity as well as the contents of phenolic acids in supernatants were estimated using HPLC-DAD.

Results. The enzyme activity was evaluated using methyl ferulate exclusively, but p-coumaric acid and another chromatographic peak (probably caffeic acid, but its identity was not positively confirmed by the DAD analysis) were present in reaction mixtures containing the supernatants of Lactobacillus acidophilus K1 cultivars with methyl p-cou­marate or methyl syringate. Both peaks of p-coumaric acid and another phenolic compound were also present in the solutions containing the supernatants of B. catenulatum and B. longum grown in the presence of methyl vanillate and the supernatants of B.animalis Bi30 grown using methyl p-coumarate, methyl syringate or methyl vanillate.

Conclusions. The results suggest a distinct ability of the studied LAB strains to transform free ferulic acid yielding p-coumaric acid and probably caffeic acid although no mechanism involved in this transformation was proposed and closer characterised in the frames of this work.